Gland seal assembly housing

ABSTRACT

A housing for a gland seal assembly, the housing comprising a main body having a bore therethrough for receiving a rotatable shaft. The main body includes first and second parts each having a packing receiving zone within the bore, each of said first and second parts including an abutment wall which forms and end wall of the packing receiving zone, and adjustment means which is operable to cause relative movement between the abutment walls in the axial direction of the bore.

BACKGROUND OF THE INVENTION

1. Field of the invention

This invention relates generally to a seal assembly for pumps and wereparticularly, though not exclusively to centrifugal slurry pumps.

2. Discussion of the Related Art

Gland seal assemblies have been used on centrifugal water and slurrypumps for many years. Typical conventional gland assemblies are shown inFIGS. 1, 2 and 3 FIGS. 1, 2 and 3 are partial schematic sectionalelevations of conventional gland seal assemblies. Such assembliesgenerally consist of an outer housing 2 which is normally called thestuffing box, with a cylindrical bore 4, through which passes arotatable shaft 50 which may for example be, a pump shaft. An end wall35 is disposed at one end of the bore. Shaft 50 may or may not have aprotective sleeve thereon. The annular gap between the bore 4 and theshaft 50 is typically filled with packing 5 which may be in the form ofa number of packing rings 8. The packing material can vary dependingupon the application but is normally woven from fibres in a square orrectangular section which can be cut into annular rings. Materials arechosen for strength and other lubricants (such as PTFE) may be added toreduce friction.

Packing 5 is normally placed into the housing or stuffing box andcompressed from the outside end by a gland 9. Due to the compressibilityof the packing 5 this allows the gap between the packing 5 and shaft (orits sleeve) 50 to be adjusted by moving the gland 9 into and out of theannular gap forming a packing space. External bolts (not shown) normallypermit this adjustment to be effected. Adjusting the gap between thestationary packing 5 and the rotating shaft 50 allows the leakage fromthe assembly to be regulated. This leakage may in certain applicationsbe critical to ensure proper cooling of the packing and shaft and toremove the heat generated by friction.

Sealing assemblies of this type for water pumps can utilize the pumpedliquid that leaks from the sealing assembly during operation to helpcool the assembly. Adequately lubricated assemblies are necessary for along life.

Slurry pumps offer an additional problem because the slurry being pumpedcontains particles. These particles cause additional friction and wearto the packing and sleeve. For slurry pumps it is common practice toinject clean sealing water from an external supply into the assembly toreduce these problems and ensure a long life. The water is injected intothe assembly via a feed channel 14 to a lantern ring assembly 10. Thelantern ring assembly may comprise a lantern ring 11 and a restrictor12. In FIG. 1 the restrictor 12 is formed of metal and in FIG. 2 it is anon-metallic device. In FIG. 3 there is a lantern ring 11 which isspaced from a neck ring 15 by a packing 8D. The lantern ring and lanternrestrictors direct the water introduced via channel 14 into a gap aroundthe shaft or sleeve thereon. This allows water into the critical gapbetween the packing 5 and the shaft 50 for proper and effectivelubrication. Both lantern ring and lantern ring restrictor arrangementsallow some sealing water to flow into the pump. This has the desiredeffect of flushing solids or particles away from the sealing assembly,hence minimising the risk of slurry contamination into the gland.

Such conventional arrangements described above have inherent problems intheir design as well as causing operational and maintenance problems forslurry pumps. It is a maintenance requirement that pumps need to berepacked (that is new fresh packings replaced for old worn packings)without the necessity of a major pump strip down. Here the small annulusaround the shaft sleeve presents a problem because it is deep and verydifficult, if not impossible to look into during repacking. Hence a lotof repacking work is done by feel. Repacking is made more difficult bythe lack of access at the back of centrifugal slurry pumps. A furtherproblem is associated with operators who do not always make properadjustments. Water supply can be variable or even fail leading to wearand failure of the packings and sleeve. Water can also leak around theoutside instead of the inside of the diameter of the packings.

SUMMARY OF THE INVENTION

The present invention seeks to alleviate one or more of theaforementioned problems associated with conventional sealing assemblies.

According to the present invention there is provided a housing for agland seal assembly, the housing comprising a main body having a boretherethrough for receiving a rotatable shaft. The main body includesfirst and second parts each having a packing receiving zone within thebore. Each of the first and second parts include an abutment wall whichforms an end wall of the packing receiving zone. There is a furtherprovided adjustment means which is operable to cause relative movementbetween the abutment walls in the axial direction of the bore.

The packing receiving zone may comprise the annular region or gapbetween the inner wall surface of the bore and the outer surface of therotatable shaft when in the assembled position.

Each abutment wall may comprise a flange extending generally radiallyinward with respect to the inner wall surface of the bore. Preferably,the abutment flanges are formed on the first and second parts of thehousing. When in the assembled position these abutment walls are remotefrom one another. The bore in each part of the housing may open towardsone another and the parts may be slightly spaced apart so as to receivea lantern ring assembly therebetween.

Preferably, each of the abutment flanges has a free inner edge which isdisposed adjacent the surface of the shaft when in the assembledposition and can function as would a restrictor. In another arrangement,neck rings may be disposed at opposite ends of the packing receivingzone between the abutment wall and the packing. Advantageously, aplurality of packing rings are disposed within each part of the housing.

One part of the housing is preferably secured to the pump casing withthe other part being operatively connected thereto so that it can moveaxially relative to that first mentioned section as a result ofoperation of the adjustment means.

The adjustment means may be in the form of a plurality of threaded boltsinterconnecting the first and second parts of the housing so thatrotation thereof causes the axial movement of the two parts.Furthermore, at least one of the parts of the housing comprises twosections interconnected by bolts and arranged so that the two parts canbe separated to facilitate ease of access and dismantling of thehousing.

The gland seal assembly may include at least two packing rings and apacking sleeve surrounding the packing rings arranged so that axialcompression of the packing sleeve can be translated at least in part toradially compression onto the packing rings. The packing sleeve maycomprise an elastomeric ring disposed between the packing rings and theinner surface of the bore. The sleeve may be in the form of an annularring forming an outer rim wall or may additionally include a radiallyinwardly extending side wall at one end of the rim wall.

Two groups of packing rings may be provided each group having associatedtherewith one of the aforementioned packing sleeves. The groups ofpacking rings may be spaced from one another by a lantern ring or thelike.

BRIEF DESCRIPTION OF THE DRAWINGS;

In one preferred arrangement the lantern ring comprises a first portionwhich fits between the two groups of packing rings and a second portionconfigured so as compress the packing sleeves when in the mountedposition. There may further be provided an 0-ring or like elementproviding a seal between the lantern ring and the housing.

Preferred embodiments of the invention will hereinafter be describedwith reference to the accompanying drawings and in those drawings:

FIGS. 1-3 are schematic partial side cross-sectional views of gland sealassemblies according to the prior art.

FIG. 4 is a schematic partial side elevation of a gland seal assemblyincorporating a housing according to the present invention;

FIG. 5 is a front elevation of the gland seal assembly shown in FIG. 4;

FIG. 6 is a similar view to FIG. 4 showing a modified form of packingassembly; and

FIGS. 7 to 9 are various modified forms of lantern ring suitable for usein the assembly of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 4, 5 and 6, it can be seen that the assembly of thepresent invention comprises certain features similar to conventionalseal assemblies and where possible like reference numerals have beenused to described like parts. The aim of any sealing assembly for a pumpis in essence, to contain the pressurized pump fluid. Pressure is brokendown by the sealing assembly so that pressure is at atmosphere outsidethe seal.

The sealing housing or stuffing box 2 has a bore 4 essentially parallelto the rotatable shaft 50 and forms an annular chamber 7. The housing 2comprises a main body 3 comprising a first part 3A and a second part 3B.Abutment walls in the form of flanges 14 and 15 are provided, eachhaving an inner edge 16 and 17. The inner diameter of the stuffing boxcomes into a diameter close to the shaft. The edges 16 and 17 arearranged so as to act as a restrictor gap to assist water flushing awayslurry. The abutment walls 14 and 15 also forms a shoulder to supportthe packings 5. The housing or stuffing box would normally be metallic,although other suitable materials could be used. It may be possible toproduce the part from a low wearing material such as High Chrome Iron asit is subject to wear by the slurry.

The shaft 50 would typically be protected by a hard metallic or coatedsleeve to minimize wear.

The two parts 3A and 3B of the housing body 3 are arranged such thatadjustment means in the form of bolts 21 permit the position of the twohousing parts to be adjusted axially relative to one another and thus,varying the compression on the packings 5 and hence controlling the gapbetween the packings and sleeve or shaft and consequently the leakage inthe seal assembly. The bolts 21 are carried on flanges 32 on housingparts 3B.

The arrangement is different to a conventional gland as the abutmentwalls do not enter the bore of the housing. Instead they form an annularseal chamber on the inside diameter. As shown housing part 3B is splitinto halves and fastened together by securing bolts 23. Part 3A may alsobe similarily split. During maintenance the housing parts can be splitand removed from around the shaft 50 thus allowing easier access to thehousing.

In the form of assembly shown a lantern ring 55 separates the two endsof the housing parts 3A and 3B. Its outer diameter locates into both thehousing or stuffing box and the bore diameters to ensure and maintainconcentricity. Typically, the lantern ring would be metallic but couldhave coatings or inserts on the inside diameter to minimise wear on theshaft or sleeve. A radial hole and annular groove on the inside diameterpermits water to be injected into the critical packing/shaft or sleevegap on both sides of the lantern ring. Thus, water can flow both intothe pump and also to the outside.

FIGS. 7 to 9 show various forms of lantern ring particularly suited foruse with the gland seal assembly of the invention. In each case thelantern ring 55 comprises a first portion 55A which fits between thegroups of packings 5 and an enlarged portion 55B which acts on thepacking sleeves 25 to partially compress them.

The new arrangement could utilise any of the conventional packing types.These are normally a woven ring cut through in one location to allowinstallation around the shaft sleeve. The number of packings 8 can varyat either end. As shown two packings are provided at each end.

Packing sleeves 25 may be incorporated around the packings 5 at eitherend of the sealing assembly. Two packing sleeves 25 are shown each beingassociated with a respective group of packing rings 8A and 8B. Thesepacking sleeves 25 have essentially elastomeric properties so that axialcompression by relative movement between the two housing parts will atfirst squeeze these sleeves axially. The sleeves shown in FIG.4.comprise an annular rim wall and those shown in FIG. 6 include a rimwall with a radially inwardly extending side wall at one end thereof. Asthe sleeves are essentially trapped between the outer housing 3 and thepackings 5, the axial compression will be translated to a radialcompression onto the packings. The packings will therefore be compressedaxially and radially and the compression will be more uniform from ringto ring. More uniform compression on each packing ring will provide afar better control over the sealing assembly and operation and leakage.The packing sleeves will also assist sealing around the outside of thepacking rings and stop uncontrolled leakage.

The arrangement as described above in accordance with the preferredembodiment, permits easier maintenance in that packing rings are moreaccessible for replacement and the length of the fixed side annular sealchamber is reduced and wear is more even.

Finally, it is to be understood that various alterations, modificationsand/or additions may be incorporated into the various constructions andarrangements of parts without departing from the spirit or ambit of theinvention.

I claim:
 1. A gland seal assembly for a slurry pump, said gland sealassembly comprising:a pump casing; and a housing having a main bodyincluding a bore therethrough for receiving a rotatable shaft, said mainbody being comprised of a fast part and a second part, one of said partsbeing secured to said pump casing, each of said first and second partshaving a packing receiving zone defined by said bore, said packingreceiving zones, in the assembled position, define an annular gapbetween an inner wall surface of said bore and an outer surface of saidrotatable shaft, said first part and said second part being spaced apartfrom one another, each of said first and second parts further includinga radially extending abutment flange, each abutment flange forming anend wall for the respective packing receiving zone, said abutmentflanges being disposed remote from one another in the assembledposition; at least one packing ring being disposed within each of saidpacking receiving zones; a lantern ring assembly disposed between saidfirst part and said second part; and an adjustment means for causingrelative movement between said abutment flanges in the axial directionof the bore.
 2. The gland seal assembly according to claim 1, whereineach of said abutment flanges has a free inner edge which is disposedadjacent to said outer surface of said shaft in the assembled position.3. The gland seal assembly according to claim 1, further comprising aneck ring disposed within each of said packing receiving zones, saidneck ring being disposed between said respective end wall and saidpacking.
 4. The gland seal assembly according to claim 1, wherein saidadjustment means comprises a plurality of threaded bolts interconnectingsaid first part and said second part so that rotation of said boltscauses axial movement of said first and second parts, at least one ofsaid first and second parts is comprised of two sections that areinterconnected by bolts so that said two sections can be separated. 5.The gland seal assembly according to claim 1, further comprising apacking sleeve disposed within each packing receiving zone, said packingsleeve surrounding said respective at least one packing ring so thataxial compression of the packing sleeve is translated, at least in part,to a radial compression of said respective at least one packing ring,said packing sleeve comprising an elastomeric ring disposed between saidpacking ring and said inner surface of said bore, said packing sleevecomprising an annular ring having an outer ring wall.
 6. The gland sealassembly according to claim 5, wherein said packing sleeve includes aradially inwardly extending side wall disposed at one of the axial endsof said packing sleeve.
 7. The gland seal assembly according to claim 5,wherein said at least one packing ring disposed in each packingreceiving zone are spaced from one another by said lantern ring.